Abrasive article backed with stretchable-compressible material



Oct. 26, 1965 w. M. M coRD, JR 3,214,253

ABRASIVE ARTICLE BACKED WITH STRETCHABLE'COMPRESSIBLE MATERAL OriginalFiled April 18. 1960 IN V EN TOR.

ZZ/dg 7120517. fc Cora/ 5M 2M5 6W United States Patent O ABRASHVEARTICLE BACKED WITH STRETCH- ABLE-COMPRESSIBLE MATERIAL Wilfred M.McCord, Jr., Louisville, Ky., assiguor to Vermont American Corporation,a corporation of Kentucky Continuation of application Ser. No. 22,860,Apr. 18, 1960. This application June 26, 1963, Ser. No. 295,265 3Claims. (Cl. 51-297) This application is a continuation of my copendingapplication, Serial No. 22,860, filed April 18, 1960, now abandoned, andrelates to a new and improved abrasive article and a new and improvedmethod of making the same. While the article is well adapted for manualuse, it is particularly suited for machine use for removal of stock andfor surface finishing of a wide variety of materials such, for example,as woods, plastics, cements and even metals.

'Heretofore it has been common to employ sheets of paper, or sometimescloth, to which has been glued grit material in the form of grains orparticles of sand, aluminum oxide, metal carbides, diamonds and thelike. The grit material comes in various sizes and is distributed invarious densities upon the sheets. However, such sheet material,particularly when formed of paper, has had a short life because of itslack of strength and tendency to tear or crack. Also the grit materialhas a tendency to become loosened after a short working period.

While the foregoing disadvantages of prior abrasive articles may havebeen mainly an inconvenience for hobbyists and home workshop use, theyhave been an expensive addition to the cost of production in industrialoperations, not merely because of the short life of the abrasive articlebut even more so because of the down time of the machines employingthem, and the cost of labor in frequently replacing the articles.

To overcome the disadvantages of the prior articles mentioned above, amore permanent type of abrasive article has been provided in whichtungsten carbide grit is copper brazed to a thin sheet steel backing.Such an abrasive sheet is much more durable than the ordinary sandpaperand similar products, but it also has certain disadvantages. Forexample, if the edge of the thin sheet becomes dented, the sheet at thatarea becomes work hardened and it is very difiicult to eliminate thedent and return the sheet to a truly flat surface. Usually a point or aridge remains and it will undesirably scratch or scour the surface beingworked on. Denting, sharp bending, or similar deformations may occurwhether the sheet is being employed manually or in a machine.

In certain machine-uses the abrasive sheet is subjected to repeatedflexing at a limited location, more or less along a line, and results infatigue of the metal, cracking or other failure. For example, in avibrator sander at the end of each stroke there is a flexing of themetal sheet around a radius near or at the location where the metalsheet is fastened or at a location where the sheet bends around aplaten.

Accordingly, it is an object of my invention to provide an abrasivearticle having a thin sheet metal base which will be protected againstthe effects of denting, bending, flexing and the like and thereby haveits useful life increased and avoid the danger of undesirably scratchingor scouring the surface of the material which is being finished. To thatend I provide the abrasive sheet with a flexible backing secured to thesheet on the opposite side from the abrasive grit. That backing byreason of its inherent stretchability and compressibility and itsgreater thickness than the metal sheet serves to spread the stresses,resulting from abrupt contact or bending or flexing, over a greater areaof metal rather than letting 3,214,253 Patented Oct. 26, 1965 them beapplied along a line or other limited area. To put it another way, thebacking resists sharp bends.

The backing also provides a cushioning effect. The cushioning effect isuseful when heavy grinding loads are applied, quite apart from bendingstresses, since grit fracture and loss of grit is minimized. The backingmay be made of fabrics, plastic materials or rubber and of a thicknesssubstantially greater than the sheet steel base. I have found that atightly woven cotton or other fabric will provide substantial body tothe overall article and will stretch or compress as the article is bentor deflected. Any suitable adhesive which is bendable will besatisfactory for joining the backing to the sheet metal base. A rubberbacking may be vulcanized to the base.

There is another advantage to the backing particularly when the abrasivearticle is used in the form of a belt on a belt sander. Most beltsanders have the belt moving over a steel platen and excessive wear canoccur on the platen and belt if a steel belt is used directly in contactwith the platen. Fire hazard is also a factor when steel belts are useddirectly at high speed over a steel platen. The backing materialtherefore will not only provide resilience in passing over the platenbut will eliminate steehto-steel contact. The same advantages alsoinhere when using the abrasive article of my invention in reciprocatingplaten type of panel sanders.

Other uses and advantages of my invention will become apparent or beobvious from the following drawings when taken in connection with thewritten description. In the drawings:

FIGURE 1 is a perspective view of an abrasive article in the form of asheet, the relative thicknesses of the parts of the article not being intrue proportion because of the difficulty of depicting the relativethinness of the sheet metal base;

FIGURE 2 is an enlarged fragmentary cross sectional view of the articleof FIGURE 1 showing the thickness of the parts in truer proportion; and

FIGURE 3 is a diagrammatic showing of a method of forming the article.

Referring now to FIGURES 1 and 2 an abrasive article in the form of asanding sheet is indicated generally by the reference numeral 10 and itconsists of a thin sheet metal base 11 to which is secured by anadhesive material 12 a flexible backing 13. On the side of the sheetmetal base opposite from the backing 13 is secured grit material such astungsten carbide particles. The grit is preferably copper brazed as at15 to the base 11. The amount of copper needed for brazing the particlesto the base is very little as is known in the brazing art and theparticles are secured very strongly to the base 11. The sheet metal base11 is preferably made of steel and may vary in thickness from about .001inch to about .008 inch while the flexible backing, in the form of afabric such as a rather tightly woven cotton may be of a thickness rangeof about .006.060 inch. Preferably the fabric should be in the ratio ofat least approximately 5-1 relative to the sheet metal base. Whileplastics or rubber vulcanized to the sheet metal base woulld also give aresilience and serve as a suitable backing to prevent sharp bending orother deformation of the sheet metal, I have found that fabric is verysatisfactory. It has a stretchability and compressibility as well as acushioning effect which very satisfactorily distribute any bendingforces over a suificiently large area of the sheet metal base as toavoid sharp bends which would tend to fatigue or crack the metal,particularly if the bending forces are repeated as may be the case whenthe abrasive article is used in sanding machines of various types. Alsothe fabric backing has a lower coeflicient of friction relative to asteel platen than would be the case with a rubber backing for example.

The adhesive 12 may be a commercial form such as the product identifiedas EC-1390 and manufactured under U.S. Patents 2,610,910 and 2,918,442.EC-1390 is a solvent type adhesive cement composition comprising a blendof polychloroprene and a normally solid phenoaldehyde resin, such as acondensation product of formaldehy'de and para-tertiary butyl phenolpreferably within the proportions indicated in the aforesaid twopatents. The adhesive of that type may be sprayed on, but it will beappreciated that the adhesive may be applied by a brush or silk screen.Various adhesives may be employed and some may be thermo-setting and, toa degree, pressure sensitive after being applied such for example as amodified phenolic resin adhesive.

When producing the abrasive article by a continuous method such asillustrated in FIGURE 3, it is preferred to spray on the adhesive.Therefore, while some adhesives would be suitable for painting or silkscreening onto the backing member and onto the sheet metal base, theywould not be as suited for a continuous process in forming the abrasivearticle as a long strip or belt.

Turning now to FIGURE 3, the sheet metal base consisting of a long thinsteel strip 11, which may be drawn from a roll (not shown), is firstspray coated on the side having the grit in order to give a pleasingcopper-lacquered finish. That finish however, is for appearance and isnot in any way a bonding means for the grit. I prefer to spray that ontothe grit side of the sheet metal base by a spraying mechanism 16 whichis positioned at a location ahead of the mechanism for spraying theadhesive on the opposite side of the sheet metal base which latterspraying mechanism is diagrammatically indicated at 17. A Web or stripof woven, or other fabric backing material 13' from a roll (not shown)may have the adhesive sprayed on it by a spraying mechanism 18 With thelatter mechanism either being spaced from spraying mechanism 17, asshown, or disposed substantially adjacent mechanism 17. I have foundthat the two spraying mechanisms 17 and 18 need not be juxtapositionedin order for the bonding to be satisfactory.

After the fabric backing 13 and the sheet metal strip 11' have had thespray coating of adhesive they become slightly tacky prior to beingpassed together in overlying relationship through a pair of rollers 19which press the two strips together so that the adhesive may bond them.Any suitable aligning means may be provided for guiding the strips 11'and 13', and the rollers 19 may serve as the means for drawing strips11' and 13 from their rolls. With some adhesives it may be desirable tohave the rollers heated, but with the Minnesota Mining and ManufacturingCompany adhesive EC1390, that is not necessary. The abrasive strip withthe backing bonded to the sheet metal base may then be coiled up on asuitable support 20 by guide means (not shown). I prefer to coil thestrip with the fabric backing outside since it has 4 greaterstretchability and there is less likelihood of slip between the base 11and backing 13.

While I prefer to carry on the lacquer spraying and the adhesivespraying continuously and simultaneously at separated points along thetravel path of the sheet metal base strip, it will be appreciated thatthe lacquer coating might be entirely done first or it might be doneafter the backing is secured to the sheet metal base. Also, While Iprefer to spray adhesive to both the backing 13 and the base 11',bonding could be performed by spraying one or the other of the adjoiningsurfaces of the sheet metal base or fabric backing.

It will be appreciated that variations in the article and method ofmaking the same are possible, in the light of my disclosure, and I donot intend to be limited to the specific article or method illustratedor described except insofar as the claims appended hereto are solimited.

I claim:

1. An abrasive article of manufacture comprising a relatively thin sheetof steel providing a generally planar working surface on one side andbeing of generally uniform thickness and being normally non-stretchablein use but being subject upon sufiicient impact or bending to becomepermanently deformed out of the plane of the working surface, and saidthin sheet having a flat marginal portion exposed during usage to suchpossible de formation of the working surface, abrasive grit particlescopper brazed to said one side of said thin sheet, and flexibledeformation-resisting backing means of stretchable and compressiblenon-metallic material adhering to and overlying the other side of saidthin sheet but not extending beyond its marginal portion, said backingmeans being coextensive with the thin steel sheet and having sufficientbulk as to distribute bending forces exerted on the steel sheet over alarge area, the thickness range of the thin steel sheet beingapproximately 001-008 inch and that of the backing being approximately.006.060 inch and at least five times the thickness of the thin sheetsheet.

2. The article of claim 1 wherein the backing means adhering to the thinsteel sheet is of woven fabric.

3. The article of claim 1 wherein the backing means adhering to the thinsteel sheet is rubber.

References Cited by the Examiner UNITED STATES PATENTS 2,128,906 9/38Benner et al. 51-298.1 2,187,743 1/40 Kirchner et al. 5-1-2981 2,252,5878/41 Tone et al. 51298.1 2,906,612 9/59 Anthony et al 51-309 3,014,79512/61 Schmidlin 51297 ALEXANDER H. BRODMERKEL, Primary Examiner.

MORRIS LIEBMAN, Examiner.

1. AN ABRASIVE ARTICLE OF MANUFACTURE COMPRISING A RELATIVELY THIN SHEETOF STEEL PROVIDING A GENERALLY PLANAR WORKING SURFACE ON ONE SIDE ANDBEING OF GENERALLY UNIFORM THICKNESS AND BEING NORMALLY NON-STRETCHABLEIN USE BUT BEING SUBJECT UPON SUFFICIENT IMPACT OR BENDING TO BECOMEPARMANENTLY DEFORMED OUT OF THE PLANE OF THE WORKING SURFACE, AND SAIDTHIN SHEET HAVING A FLAT MARGINAL PORTION EXPOSED DURING USAGE TO SUCHPOSSIBLE DEFORMATION OF THE WORKING SURFACE, ABRASIVE GRIT PARTICLESCOPPER BRAZED TO SAID ONE SIDE OF SAID THIN SHEET, AND FLEXIBLEDEFORMATION-RESISTING BACKING MEANS OF STRETCHABLE AND COMPRESSIBLENON-METALLIC MATERIAL ADHERING TO AND OVERLYING THE OTHER SIDE OF SAIDTHIN SHEET BUT NOT EXTENDING BEYOND ITS MARGINAL PORTION, SAID BACKINGMEANS BEING COEXTENSIVE WITH THE THIN SHEET AND HAVING SUFFICIENT BULKAS TO DISTRIBUTE BENDING FORCES EXERTED ON THE STEEL SHEET OVER A LARGEAREA, THE THICKNESS RANGE OF THE THIN STEEL SHEET BEING APPROXIMATELY.001-.008 INCH AND THAT OF THE BACKING BEING APPROXIMATELY .006-.060INCH AND AT LEAST FIVE TIMES THE THICKNESS OF THE THIN SHEET SHEET.